package summer_vacation.xuqianlan;
import java.util.Scanner;
/**
 * Created by lenovo on 2015/9/5.
 */
public class Test_39 {
    public static void main(String[] args) {
        Scanner input=new Scanner(System.in);
        double n=input.nextDouble();
       double sum=0;
        double s=0;
        for(double i=1;i<=n;i++){
            sum+=i;
            s+=1/sum;

        }
        System.out.println("1+1/(1+2)+1/(1+2+3)+....1/(1+2+3...+n)....="+s);
    }
}
